Infinity system preamp??

[bk7374]

I've a 95 B2500 full size conversion van. A Chrystar conversion. It has an Infinity system that keeps blowing the speaker circuit fuse. The same circuit has the horn on it. It's tough following wires but some one told me that this system may have a preamp that is bad. Do these systems have pre amps and where would they put it? Also, are these speakers amplified and wouldthat cause the fuse to blow? Is there an easy test to check if the head unit is ok or putting out too much juice?